In Situ Tumor Vaccination Using Lipid Nanoparticles to Deliver Interferon-β mRNA Cargo.

In situ cancer vaccination is a therapeutic approach that involves stimulating the immune system in order to generate a polyclonal, anti-tumor response against an array of tumor neoantigens. Traditionally, in situ vaccination approaches have utilized adenoviral vectors to deliver immune-stimulating genes directly to the tumor microenvironment. Lipid nanoparticle (LNP)-mediated delivery methods offer several advantages over adenoviral delivery approaches, including increased safety, repeated administration potential, and enhanced tumor microenvironment activation. To explore in situ vaccination using LNPs, we evaluated LNP-mediated delivery of a reporter gene, mCherry, and an immune-stimulating gene, IFNβ, in several in vitro and in vivo models of lung cancer. In vitro experiments demonstrated successful transfection of murine cancer cell lines with LNPs carrying both mCherry and IFN-β mRNA, resulting in high expression levels and IFNβ production. In vivo studies using LLC.ova flank tumors showed that intratumoral injection of IFNβ-mRNA LNPs led to significant IFNβ production within the tumor microenvironment, with minimal systemic exposure. Therapeutic efficacy was evaluated by injecting established LLC.ova flank tumors with IFNβ-mRNA LNPs bi-weekly for two weeks. Treated tumors showed significant growth inhibition compared to controls. Flow cytometric analysis of tumor-infiltrating leukocytes revealed that tumors injected with IFNβ-mRNA LNPs were associated with an increased CD8:CD4 T-cell ratio among lymphocytes, more CD69-expressing CD8 T-cells, and an increased presence of M1 macrophages. Efficacy and an abscopal effect were confirmed in a squamous cell carcinoma model, MOC1. No toxicity was observed. These findings show that intratumoral LNP delivery of immune-stimulating mRNA transcripts, such as IFNβ, can effectively stimulate local anti-tumor immune responses and warrants further investigation as a potential immunotherapeutic approach for cancer.